1. Field of the Invention
The present invention relates to a method of controlling the withdrawal of gas from a refuse dump via gas collection mechanisms disposed at a distance from one another in various locations in the refuse or garbage. The gaseous decomposition products are conveyed from the gas collection mechanisms to a gas collector, and are then supplied to the consumer via a delivery pipe. The present invention also relates to an apparatus for withdrawing the gaseous decomposition products from the refuse dump, in which refuse or garbage is deposited in a substantially gastight chamber. The gas collection mechanisms are disposed at a distance from one another in various locations in the refuse or garbage, with the gas decomposition products being withdrawn from the gas collection mechanisms via gas withdrawal lines.
In a refuse dump, decay results in gaseous decomposition products that to a large extent contain methane gas. Methane is an inflammable gas, which can lead to fires in the refuse dump. If methane enters a closed space, the danger of explosion exists if the CH.sub.4 content in the air reaches 5-15%. If the gaseous decomposition products escape from the refuse dump into the surrounding ground, the methane damages the plants. One must therefore endeavor to withdraw the gaseous decomposition products, and to make them usable from an energy standpoint or burn them off.
2. Description of the Prior Art
It is known from German Patent Applications P 34 24 788.8 and P 34 25 785.3 to deposit the refuse in a chamber. Provided in the refuse are gas collection mechanisms in the form of a gas-drainage-pipe system or in the form of gas wells. The gaseous decomposition products enter these gas collection mechanisms, and are withdrawn from the dump via gas withdrawal lines. A conveying mechanism, such as a pump, blower, etc., conveys the gaseous decomposition products via a delivery pipe to a consumer for commercial use.
It has become evident in practice that even if the chambers are covered, air can be drawn into the refuse. If more gas is withdrawn from the gas collection mechanisms than can subsequently flow out of the refuse, a pressure differential results that favors an increased penetration of air. However, because of the air that is flowing in, too much oxygen enters the refuse, thus impairing, and under unfavorable conditions even destroying, the conditions essential for the life of the bacteria that release the usable methane. The formation of methane is then reduced or is even completely halted. Under certain circumstances, the CH.sub.4 content in the withdrawn gas stream is reduced to such an extent that it is no longer possible to commercially utilizizes the gas.
In contrast, if fewer gaseous decomposition products are withdrawn than are produced, these gases can escape in an uncontrolled manner into the surroundings, and can produce a permanent danger of explosion. Gaseous decomposition products that pass into the ground damage the surrounding flora. Again, an optimum gas utilization does not result.
An object of the present invention is to withdraw the gaseous decomposition products from a refuse dump in a controlled manner in order, on the one hand, to avoid the penetration of air into the refuse, and on the other hand, to prevent an uncontrollable escape of the gaseous decomposition products from the dump; furthermore, the withdrawn gaseous decomposition products should at all times have an optimally usable methane content.